Reverse emulsions for cavity control

ABSTRACT

Injection fluids formed of reverse emulsions and related methods of forming and using reverse emulsions for cavity control in solution mining. The reverse emulsion can reduce the volume of oil required to create an oil pad at the roof of a solution mining cavern in order to prevent vertical leaching and cavern collapse. The reverse emulsion can be formed from an emulsifier, a brine solution and oil. The emulsifier concentration can range from about 1% to about 5% by weight of the reverse emulsion. The emulsifier and the oil can be combined to form an oil/emulsifier mixture, wherein the oil/emulsifier mixture is combined with the brine solution to form the reverse emulsion. The oil/emulsifier mixture can be from about 1% to about 5% by weight of the reverse emulsion.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/695,870filed Nov. 26, 2019, which in turn is a continuation of application Ser.No. 16/015,372 filed Jun. 22, 2018, now U.S. Pat. No. 10,508,529 issuedDec. 17, 2019, which in turn is a division of application Ser. No.15/158,970 filed May 19, 2016, now U.S. Pat. No. 10,012,066 issued Jul.3, 2018, which claims the benefit of U.S. Provisional Application No.62/163,486 filed May 19, 2015, each of which is hereby incorporatedherein in its entirety by reference.

FIELD OF THE INVENTION

Embodiments of the present invention are generally directed to the useof reverse emulsions for cavity control. Specifically, embodiments ofthe present invention are directed to materials and methods forincreasing cavern stability and controlling leaching using reverseemulsions during solution mining.

BACKGROUND OF THE INVENTION

Solution mining, also referred to as in-situ leach mining, is a commonlyused method for extracting water-soluble salts such as sylvite (i.e.,potash) halite (i.e., sodium chloride), and sodium sulfate. It is alsoused as a method for producing underground storages cavities for liquidhydrocarbons, compressed natural gas, and waste products. In its mostbasic form, solution mining requires a cased and cemented borehole,generally comparable to gas or oil wells, which connects a surface plantto the area of water-soluble salt formation (i.e., a salt deposit).Water-based fluids or solvents are injected through the borehole andsalt is dissolved from the salt formation to form brine. The brine isthen brought back up to the surface for processing. Solution mining isoften used in situations where the deposits are too deep or too thin forconventional mining techniques, and solution mining generally createsminimal surface disturbance and little waste compared to conventionalmining. Other advantages of solution mining include the fact thatimpurities in the mined salt can be readily removed from the brine,which allows for production of high-grade salt for other uses, includingfood, chemical, and pharmaceutical manufacturing. Additionally, anyimpurities (i.e., insolubles) are readily disposed of by reinjectingthem into the cavern. Furthermore, brine is easily transportable and isoften times the required form of raw material in some chemicalmanufacturing processes.

Effective solution mining requires the creation and maintenance of astable cavern that will remain intact over the course of the leachingperiod, typically 2-5 years. During the leaching period, the shape ofthe cavern can be influenced by several parameters, such as the leachingrate, the amount of water or solvent injected, the depths of theleaching equipment, and the duration of the leaching intervals. Oftentimes the roof or upper portion of the cavern is protected by a pad ofcrude oil. This oil pad is applied to ensure that leaching with, forexample, injected water, occurs horizontally only, rather thanvertically into the cavern roof If water is allowed to leach vertically,high concentrations of salt will not be achieved, and the cavern roofwould be more likely to collapse.

The use of a pad of oil to mitigate the risks associated with thecreation and maintenance of cavity control is quite expensive. One wayto reduce this expense would be to reduce the amount of oil required foreffective cavity control. For example, one such method could involve theuse of emulsions, in particular, reverse emulsions. Emulsions aremixtures of two or more liquids in which particles or droplets of anonpolar liquid (e.g., oil) are dispersed in a polar medium (e.g.,water). Reverse emulsions are typically mixtures of droplets of a polarliquid in a nonpolar medium. The stability of an emulsion or a reverseemulsion depends on the liquids used to create it. Emulsion stabilityrefers to the ability of an emulsion to resist change in its propertiesand internal-phase bubble size over time. In order to counteract thetendency of emulsions and reverse emulsions to become destabilized, anappropriate surface active agent (i.e., surfactant) or emulsifier, canbe used. Generally, surfactants or emulsifiers increase the kineticstability of an emulsion so that the size of the droplets does notchange significantly over time.

Given the widespread use of solution mining, there remains a need todevelop efficient and economical materials and methods to maintaincavity control during the leaching process, which can last as long asfive years. More specifically, there remains a need to develop materialsand methods to reduce the volume of oil required to create the oil padat the roof of the cavern in order to prevent vertical leaching andcavern collapse.

SUMMARY OF THE INVENTION

Embodiments of the present invention are generally directed to the useof reverse emulsions for cavity control. Specifically, the presentinvention is directed to materials and methods for increasing cavernstability and controlling leaching using reverse emulsions duringsolution mining.

In some embodiments, the present invention relates to a process forsolution mining using a reverse emulsion comprising oil, brine, andemulsifiers, wherein the reverse emulsion occupies the upper portion orroof of a cavern. The oil of the reverse emulsion can comprise anunprocessed or unused and/or reprocessed crude oil or fractions thereofincluding, but not limited to, heavy crude oil fractions such as heavydistillates, light crude oil, or combinations thereof. The brine of thereverse emulsion can comprise, for example, about 25% and about 100%saturation of salts, and more particularly between about 25% and about75% saturation of salts, The salts can comprise, for example, potassiumchloride (KCl), sodium chloride (NaCl), and/or calcium chloride (CaCl₂).The total brine including salts, insolubles such as clays, and water,make up a final concentration of between about 30% to about 80% of thereverse emulsion. The emulsifier of the reverse emulsion can comprisepolyisobutylene succinic anhydride (PIBSA) at a final concentration ofabout 1 to about 5 weight percent (wt %) of the reverse emulsion. Insome embodiments, use of a reverse emulsion in the above compositionranges can reduce the amount of oil typically used in solution miningbetween about 30% to about 80%.

In embodiments, the present invention relates to a method for creating areverse emulsion comprising oil, brine, and emulsifiers for use in asolution mining process, wherein the reverse emulsion occupies the upperportion or roof of a cavern. The reverse emulsion can be created byadding an emulsifier or a surfactant to a source of oil, such as, forexample, an unprocessed or unused and/or reprocessed oil. Examples ofunprocessed oil can comprise refined crude oil or fractions thereofincluding, but not limited to, heavy crude oil fractions such as heavydistillates, light crude oil, or combinations thereof. Examples ofreprocessed oil can comprise reprocessed crank case oil and/or othertypes of motor and engine oil, recovered heavy distillates, and thelike.

In an embodiment, the final concentration of the emulsifier is betweenabout 1 wt % and about 5 wt %.

The oil and emulsifier mixture can then be combined with brine usinghigh energy mixing, such that the mixing creates small particles ordroplets of brine (e.g. 0.5-2 μm or smaller in size) that are suspendedin the oil and stabilized by the emulsifier. In some cases, the brine ofthe reverse emulsion can comprise, for example, about 25% and about 100%saturation of salts, and more particularly between about 25% and about75% saturation of salts, such as, for example, potassium chloride (KCl),sodium chloride (NaCl), and/or calcium chloride (CaCl₂). The brine canfurther include insolubles such as clays, and water, the brine being ata final concentration of between about 30% to about 80% of the reverseemulsion. The oil of the reverse emulsion can comprise an unprocessed orunused and/or reprocessed crude oil as described above. In other cases,the emulsifier of the reverse emulsion can comprise polyisobutylenesuccinic anhydride (PIBSA) at a final concentration of about 1 wt % toabout 5 wt % of the reverse emulsion. In some embodiments, the use of anemulsifier in the above composition range can produce a stable reverseemulsion such that the brine particles stay in suspension for longerthan five years.

In other embodiments, the present invention relates to a process forsolution mining using a reverse emulsion comprising oil, brine, andemulsifiers, wherein the reverse emulsion is injected into a cavern suchthat the reverse emulsion occupies the upper portion or roof of thecavern, thereby increasing cavern stability and preventing or reducingvertical leaching. The oil of the reverse emulsion can comprise anunprocessed or unused and/or reprocessed crude oil or fractions thereofas described above. In some embodiments, the brine of the reverseemulsion can comprise a solution of potassium chloride (KCl), sodiumchloride (NaCl), and/or calcium chloride (CaCl₂), insolubles such asclays, and water, such that the brine has a final concentration ofbetween about 30% to about 80% of the reverse emulsion. The brine cancomprise, for example, about 25% and about 100% saturation, moreparticularly between about 25% and about 75% saturation. In oneparticular non-limiting embodiment, the reverse emulsion can comprisebrine comprising a salt solution at about 70% saturation.

In some embodiments, the emulsifier of the reverse emulsion can comprisepolyisobutylene succinic anhydride (PIBSA) at a final concentration ofabout 1 wt % to about 5 wt % of the reverse emulsion. In someembodiments, a reverse emulsion in the above composition ranges can beinjected into a cavern at a temperature ranging from about 120F to about200F, and more particularly, from about 130F to about 150F.

The solution mining materials and methods described above are notlimited to the mining of salt. The materials and methods according toembodiments can be used with any types of solution mining processes andsystems. The above summary of the various representative embodiments ofthe invention is not intended to describe each illustrated embodiment orevery implementation of the invention. Rather, the embodiments arechosen and described so that others skilled in the art can appreciateand understand the principles and practices of the invention. Thefigures in the detailed description that follow more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE FIGURES

Subject matter hereof may be more completely understood in considerationof the following detailed description of various embodiments of thesubject matter in connection with the accompanying drawings, in which:

FIG. 1 is a diagram of a solution mining cavern, according to anembodiment of the invention.

FIG. 2 is a diagram of a reverse emulsion composition, according to anembodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

As shown in FIG. 1, a non-limiting exemplary embodiment of a system andmethod for a solution mining process (also referred to as in-situ leachmining), reverse emulsions comprising oil, brine, and emulsifiers can beused to increase cavern stability and to control leaching during thesolution mining process. In this non-limiting embodiment, solutionmining cavern 100 generally comprises a layer of high grade material tobe mined, for example, high grade potash 110, that lies above salt bed115. During the solution mining process, borehole 120 is used as a meansfor injecting fluid into the cavern, and for extracting the resultingbrine. This extraction process is also referred to as leaching.Typically, brine is a highly concentrated solution of water and salt(e.g., in potash mining, brine is specifically a solution of water andpotassium chloride). Brine can be created when potash is extractedduring solution mining. Aqueous solutions and other solvents can beinjected through borehole 120, dissolving various salts from the saltformation to form brine. The brine can then be brought back up to thesurface for processing, while any insoluble impurities 125 settle overtime at the bottom (sump) of the cavern. In some cases, separateboreholes can be used for injection and extraction purposes, dependingon the material being mined and the composition of the mine. Generally,borehole 120 is cased and cemented and connected to a surface plantwhere the extracted brine can be processed. Solution mining is oftenused in situations where the deposits are too deep or too thin forconventional mining techniques, and solution mining generally createsminimal surface disturbance and little waste compared to conventionalmining.

In some embodiments, the creation and maintenance of solution miningcavern 100 can involve the use of oil pad 130 on upper portion or roof135 of cavern 100. Generally, oil pad 130 prevents vertical leaching ofthe injected fluid during the leaching period, which can last over 5years. The presence of oil pad 130 in a solution mine can ensure thatleaching with, for example, injected hot water, occurs horizontally onlywithin the layer of high grade potash 110, rather than vertically intocavern roof 135. If water is allowed to leach vertically, highconcentrations of salt will not be achieved, and cavern roof 135 may bemore likely to collapse.

The use of oil pad 130 for solution mining, although effective atincreasing cavern stability and controlling leaching, can be veryexpensive due to the oil cost itself. It would therefore be beneficialand more economical to reduce the amount of oil required to create anoil pad for solution mining. In an embodiment of the present invention,solution mining can involve the use of reverse emulsions comprising oil,brine, and emulsifiers for purposes of oil volume extension in an effortto reduce the volume of oil required without sacrificing effectiveness.Emulsions are mixtures of two or more liquids in which particles ordroplets of a nonpolar liquid (e.g., oil) are dispersed in a polarmedium (e.g., water). Reverse emulsions are typically mixtures ofdroplets of a polar liquid in a nonpolar medium. The stability of anemulsion or a reverse emulsion depends on the liquids used to create it.In some cases, a reverse emulsion comprising oil, brine, and emulsifierscan be injected into a solution mine cavern such that it occupies theupper portion or roof of the cavern.

The reverse emulsion can comprise oil from any suitable source, such as,for example, an unprocessed or unused and/or reprocessed oil. Examplesof unprocessed oil can comprise refined crude oil or fractions thereofincluding, but not limited to, heavy crude oil fractions such as heavydistillates, light crude oil, or combinations thereof. Examples ofreprocessed oil can comprise reprocessed crank case oil and/or othertypes of motor and engine oil, recovered heavy distillates, and thelike.

The reverse emulsion can also comprise brine having variousconcentrations of salt up to the point of saturation (i.e., percentsaturation). For example, the reverse emulsion can comprise brinecomprising salts between about 25% and about 100% saturation. In somecases, the reverse emulsion can comprise brine comprising salts betweenabout 25% and about 75% saturation. In other cases, the reverse emulsioncan comprise brine comprising salts at about 70% saturation. The reverseemulsion can also comprise brine comprising various soluble andinsoluble salts. For example, the reverse emulsion can comprise brineincluding potassium chloride (KCl), sodium chloride (NaCl), and/orcalcium chloride (CaCl₂), insoluble salts such as calcium sulfate(CaSO4)/anhydrite, magnesium chloride (MgCl₂), dolomite, magnesiumsulfate, silica, quartz, illite, sepchlorite, kaolinite, calcitephosphates, or any other insoluble salts associated with any evaporativemember or formation, or any combination thereof.

In some cases, the reverse emulsion can comprise brine formed of asolution of calcium chloride (CaCl₂), potassium chloride (KCl), sodiumchloride (NaCl), or combinations thereof such that the solution ofsoluble salts is between about 50% and about 75% saturated. In othercases, the reverse emulsion can comprise brine comprising a solution ofpotassium chloride and sodium chloride such that the solution of solublesalts is less than about 70% saturated. Regardless of the composition ofthe brine, embodiments of the reverse emulsion can comprise brine at afinal concentration of between about 30% and about 80% of the reverseemulsion. In some cases, the reverse emulsion can comprise brine at afinal concentration of between about 50% and about 70% of the reverseemulsion.

The reverse emulsion can also comprise an emulsifier (also referred toas a surfactant) from any suitable source, such that the presence of theemulsifier counteracts the tendency of the reverse emulsions to becomedestabilized. Generally, surfactants or emulsifiers increase the kineticstability of an emulsion so that the size of the droplets (e.g. 0.5-2μm) does not change significantly over time. In some cases, the reverseemulsion can comprise an emulsifier comprising polyisobutylene succinicanhydride (PIBSA) as commercially available from suppliers such as, forexample, Lubrizol. Conventionally, PIBSA has found commercial success toform reverse emulsions in the explosives industry. Non-limiting examplesof other suitable emulsifiers can include oleic acid, phosphoric acidesters, fatty acid esters, fatty acid ethoxylates, sorbitan ester,sorbitan oleate, other fatty-acid based emulsifiers, and combinationsthereof.

In some cases, the reverse emulsion can comprise an emulsifier at afinal concentration of about 1 to about 5 weight percent (wt %) of thereverse emulsion. In other cases, the reverse emulsion can comprise anemulsifier at a final concentration of about 1.5 wt % to about 4 wt % ofthe reverse emulsion. In still other cases, the reverse emulsion cancomprise an emulsifier at a final concentration of about 3 wt % of thereverse emulsion. Using reverse emulsions of the present invention, aratio of oil savings to emulsifier expense can range from 2-10 dependingon oil cost, emulsifier cost, emulsifier concentration in reverseemulsion, and percent brine in the reverse emulsion.

In some embodiments, the present invention relates to a method forcreating a reverse emulsion comprising oil, brine, and emulsifiers foruse in a solution mining process, wherein the reverse emulsion occupiesthe upper portion or roof of a cavern. In some cases, as shown in FIG.2, reverse emulsion 200 can be created by first adding one or moreemulsifier or a surfactant to a source of oil, to produce oil andemulsifier mixture 210. The emulsifier can be added either to oil inlinewhile blending in an emulsion blender, or can be pre-mixed before theemulsion blender. In some cases, the final concentration of theemulsifier is between about 1 wt % and about 5 wt % of the reverseemulsion. In other cases, oil and emulsifier mixture 210 can comprise anemulsifier such that the emulsifier is at a final concentration of about1.5 wt % to about 4 wt % of the reverse emulsion. In still other cases,oil and emulsifier mixture 210 can comprise an emulsifier such that theemulsifier is at a final concentration of about 3 wt % of the reverseemulsion. In some cases, oil and emulsifier mixture 210 can comprise anemulsifier comprising polyisobutylene succinic anhydride (PIBSA). Inother case, suitable emulsifiers can include oleic acid, phosphoric acidesters, fatty acid esters, fatty acid ethoxylates, sorbitan ester,sorbitan oleate, other fatty-acid based emulsifiers, and combinationsthereof.

In some embodiments of the method of the present invention, as shown inFIG. 2, oil and emulsifier mixture 210 can then be combined with brineusing high energy mixing via an emulsion blender, such that the mixingcreates small particles or droplets (e.g. 0.5-2 μm) of brine 220 thatare suspended in the oil and stabilized by the emulsifier. The reverseemulsion can also comprise brine having various concentrations of saltup to the point of saturation (i.e., percent saturation). For example,the reverse emulsion can comprise brine comprising salts between about25% and about 100% saturation. In some cases, the reverse emulsion cancomprise brine comprising salts between about 25% and about 75%saturation. In other cases, the reverse emulsion can comprise brinecomprising salts at about 70% saturation. The reverse emulsion can alsocomprise brine comprising various salts. For example, the reverseemulsion can comprise brine comprising potassium chloride (KCl), sodiumchloride (NaCl), calcium chloride (CaCl₂), phosphates, or anycombinations thereof. In some cases, the reverse emulsion can comprisebrine comprising a solution of potassium chloride (KCl), sodium chloride(NaCl), and/or calcium chloride (CaCl₂), such that the solution ofsoluble salts between about 50% and about 75% saturated. In other cases,the reverse emulsion can comprise brine comprising a solution ofpotassium chloride and sodium chloride such that the solution of solublesalts is less than about 70% saturated. Regardless of the composition ofthe brine, embodiments of the reverse emulsion can comprise smallparticles or droplets of brine 220 at a final concentration of betweenabout 25% and about 75% of the reverse emulsion. In some cases, thereverse emulsion can comprise small particles or droplets of brine 220at a final concentration of between about 50% and about 75% of thereverse emulsion. In other cases, the reverse emulsion can comprisesmall particles or droplets of brine 220 at a final concentration ofbetween about 30% and about 80% of the reverse emulsion.

In some embodiments, the present invention relates to a process forsolution mining using a reverse emulsion comprising oil, brine, andemulsifiers, wherein the reverse emulsion is injected into a cavern suchthat the reverse emulsion occupies the upper portion or roof of thecavern, thereby increasing cavern stability and preventing verticalleaching. In some embodiments, a reverse emulsion can be injected into acavern at a temperature ranging from about 120F to about 200F, and moreparticularly, from about 100F to about 145F. In some cases, a processfor solution mining comprises using a reverse emulsion created by firstadding an emulsifier or a surfactant to a source of oil, includingunprocessed or unused and/or reprocessed crude oil or fractions thereofincluding, but not limited to, heavy crude oil fractions such as heavydistillates, light crude oil, or combinations thereof, such that thefinal concentration of the emulsifier is between about 1 wt % and about5 wt % of the reverse emulsion. In other cases, the oil and emulsifiermixture can comprise an emulsifier such that the final concentration ofthe emulsifier is about 1.5 wt % to about 4 wt % of the reverseemulsion. In still other cases, the oil and emulsifier mixture cancomprise an emulsifier such that the final concentration of theemulsifier is about 3 wt % of the reverse emulsion. In some cases, theoil and emulsifier mixture can comprise an emulsifier comprisingpolyisobutylene succinic anhydride (PIBSA). In other cases, suitableemulsifiers can include oleic acid, phosphoric acid esters, fatty acidesters, fatty acid ethoxylates, sorbitan ester, sorbitan oleate, otherfatty-acid based emulsifiers, and combinations thereof.

In some embodiments of the solution mining process of the presentinvention, the oil and emulsifier mixture can then be combined withbrine using high energy mixing, such that the mixing creates smallparticles or droplets of brine (e.g. 0.5-2 μm) that are suspended in theoil and stabilized by the emulsifier. The reverse emulsion can alsocomprise brine having various concentrations of salt up to the point ofsaturation (i.e., percent saturation). For example, the reverse emulsioncan comprise brine comprising salts between about 25% and about 100%saturation. In some cases, the reverse emulsion can comprise brinecomprising salts between about 25% and about 75% saturation. In othercases, the reverse emulsion can comprise brine comprising salts at about70% saturation. The reverse emulsion can also comprise brine comprisingvarious salts. For example, the reverse emulsion can comprise brinecomprising potassium chloride (KCl), sodium chloride (NaCl), and/orcalcium chloride (CaCl₂), insolubles such as clays, and water,phosphates, or any combinations thereof. In some cases, the brine isabout 50% and about 75% saturated. In other cases, the brine is lessthan about 70% saturated. Regardless of the composition of the brine,embodiments of the reverse emulsion can comprise brine at a finalconcentration of between about 25% and about 75% of the reverseemulsion. In some cases, the reverse emulsion can comprise brine at afinal concentration of between about 50% and about 75% of the reverseemulsion. In other cases, the reverse emulsion can comprise brine at afinal concentration of between about 30% and about 80% of the reverseemulsion.

In general, embodiments of the methods for creating a reverse emulsionfor solution mining having the compositions and concentrations above canreduce the amount of oil typically required to form an oil pad by about30% to about 80%, or can provide added oil pad thickness at equivalentcost. In some embodiments of these methods, an emulsifier having thecompositions and concentrations above can be used to produce a stablereverse emulsion such that brine particles stay in suspension for fiveyears or longer in an oil pad in a solution mining cavern.

It should also be appreciated that the exemplary embodiment or exemplaryembodiments are only examples, and are not intended to limit the scope,applicability, or composition of the invention in any way. Rather, theforegoing detailed description will provide those skilled in the artwith an enabling disclosure for implementing the exemplary embodiment orexemplary embodiments. It should be understood that various changes canbe made in the function and arrangement of elements without departingfrom the scope of the subject matter hereof as set forth in the appendedclaims and the legal equivalents thereof.

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are within the claims. Although subject matterhereof has been described with reference to particular embodiments,workers skilled in the art will recognize that changes may be made inform and detail without departing from the spirit and scope of thesubject matter.

Various modifications to subject matter hereof may be apparent to one ofskill in the art upon reading this disclosure. For example, persons ofordinary skill in the relevant art will recognize that the variousfeatures described for the different embodiments of the invention can besuitably combined, un-combined, and re-combined with other features,alone, or in different combinations, within the spirit of the subjectmatter. Likewise, the various features described above should all beregarded as example embodiments, rather than limitations to the scope orspirit of the subject matter. Therefore, the above is not contemplatedto limit the scope of the subject matter.

For purposes of interpreting the claims for subject matter hereof, it isexpressly intended that the provisions of Section 112, sixth paragraphof 35 U.S.C. are not to be invoked unless the specific terms “means for”or “step for” are recited in a claim.

1. A method of solution mining, comprising: providing a reverse emulsioncomprising an emulsifier, a brine solution, and a heavy hydrocarbonsource; and injecting the reverse emulsion into a solution mining cavernsuch that the reverse emulsion forms an oil pad that occupies a cavernroof.